The present invention relates to a pipe assembly incorporating means for lubricating a section of pipe as it is run into a well bore. The pipe may be casing liner, drillpipe, tubing or coil tubing. The invention also relates to a method of running in a section of pipe.
When a section of casing is run into a well it is common to employ lubricants to reduce the friction between the outer wall of the casing and the wall of the well. Typically, lubricants are pumped between the outer wall of the casing and the wall of the well. Such lubricants effectively provide only static lubrication. Once the casing is moving relative to the well the lubricants can provide effective lubrication. However, when movement is first initiated the lubricants may not provide effective lubrication and the starting torque to initiate movement of the casing string may be greater than the limits of the rig or the casing connections.
According to a first aspect of the invention, there is provided a pipe assembly for use in a wellbore having a plurality of outlets positioned about the periphery of the pipe at longitudinally spaced apart intervals for allowing fluid to pass from the interior to the exterior of the pipe, characterised in that a non-return valve is provided in each outlet, activated by a fusible link, which prevents flow from the interior of the pipe out of the outlets when activated. The fusible link may be actuated by an acid or alkaline pill.
The outlets may have fluid communication passages between the interior of the pipe and orifices of the outlets to convey fluid from within the pipe to the outlet orifices.
The pipe may be casing, liner, drill pipe, tubing or coil tubing. The outlets preferably include one way valves to ensure that fluid may only flow from the interior of the pipe out of the outlets and not in the return direction.
The outlets may preferably be provided on sub-sections joining sections of pipe. The outlets may include flexible seals provided about the outlet orifices.
There is further provided a method of running a section of pipe in a well bore comprising running a pipe assembly having outlets positioned about the periphery of the pipe at spaced apart intervals in the weelbore, and supplying lubricating fluid to the interior of the pipe at a sufficient pressure to cause lubricating fluid to exit from the outlets so as to provide effective hydrodynamic friction reduction between the pipe assembly and the wall of the well.
Preferably the pipe assembly includes a non-return valve that is actuated by a fusible link and after the casing is run and acid or alkaline pill is introduced into the interior of the pipe assembly to break the fusible link to actuate the non-return valve to prevent fluid flowing through the outlets.